3,161 research outputs found
Practice activity trends among oral and maxillofacial surgeons in Australia
© 2004 Brennan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.BACKGROUND: The aim of this study was to describe practice activity trends among oral and maxillofacial surgeons in Australia over time. METHODS: All registered oral and maxillofacial surgeons in Australia were surveyed in 1990 and 2000 using mailed self-complete questionnaires. RESULTS: Data were available from 79 surgeons from 1990 (response rate = 73.8%) and 116 surgeons from 2000 (response rate = 65.1%). The rate of provision of services per visit changed over time with increased rates observed overall (from 1.43 ± 0.05 services per visit in 1990 to 1.66 ± 0.06 services per visit in 2000), reflecting increases in pathology and reconstructive surgery. No change over time was observed in the provision of services per year (4,521 ± 286 services per year in 1990 and 4,503 ± 367 services per year in 2000). Time devoted to work showed no significant change over time (1,682 ± 75 hours per year in 1990 and 1,681 ± 94 hours per year in 2000), while the number of visits per week declined (70 ± 4 visits per week in 1990 to 58 ± 4 visits per week in 2000). CONCLUSIONS: The apparent stability in the volume of services provided per year reflected a counterbalancing of increased services provided per visit and a decrease in the number of visits supplied.David S Brennan, A John Spencer, Kiran A Singh, Dana N Teusner and Alastair N Gos
Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy
A renewed attempt to detect radio recombination lines from external galaxies
has resulted in the measurement of lines from several bright starburst
galaxies. The lines are produced by hydrogen ionized by young, high-mass stars
and are diagnostic of the conditions and gas dynamics in the starburst regions
without problems of dust obscuration. We present here detections of the lines
H91alpha and H92alpha near 8.6 GHz from the starburst nuclei in NGC 3256, NGC
4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line
emitting region as a collection of H II regions, we derive the required number
of H II regions, their temperature, density, and distribution.Comment: 6 pages, to appear in "Proc 331. Heraeus Seminar: The Evolution of
Starbursts", Bad Honnef, Germany, Aug 16 - 20, 2004, Eds: S. Huettemeister,
S. Aalto, D.J. Bomans, and E. Manthe
Dust deposition rates in the Wollongong-Port Kembla area, New South Wales, Australia
Dust deposition in the Wollongong-Port Kembla region, New South Wales, Australia, arising from local industrial and mining activities, has been of major concern since the early 1960s. Reports dealing with dust deposition rates in the region have been published by different organisations where the data have been averaged for the region. This provides a general trend for the deposition rates for the whole region without considering the trends occurring in specific locations. This study was the first to examine the trends observed at 35 individual gauges to identify more localised trends in dust deposition rates in the Wollongong-Port Kembla region, and also to try and identify the contribution of some of the possible dust sources. The coverage span of the data was from 1991-2003. These data were compared with two guidelines. The results indicated that the trend for dust deposition rates in the Wollongong-Port Kembla region is, generally, decreasing, but the patterns for different gauges varied both spatially and temporally. Several factors were suspected to influence dust deposition rates, including meteorological conditions, mainly wind direction, proximity to dust sources, dust control devices installed by industry, and other nearby activities that could affect the deposition rate measurements. Deposition rates in some residential areas exceeded the guidelines for recommended action. Further speciation and characterisation analyses of dust samples are needed to confirm their sources
PKS B1400-33: an unusual radio relic in a poor cluster
We present new arcminute resolution radio images of the low surface
brightness radio source PKS B1400-33 that is located in the poor cluster Abell
S753. The observations consist of 330 MHz VLA, 843 MHz MOST and 1398 and 2378
MHz ATCA data. These new images, with higher surface brightness sensitivity
than previous observations, reveal that the large scale structure consists of
extended filamentary emission bounded by edge-brightened rims. The source is
offset on one side of symmetrically distributed X-ray emission that is centered
on the dominant cluster galaxy NGC 5419. PKS B1400-33 is a rare example of a
relic in a poor cluster with radio properties unlike those of most relics and
halos observed in cluster environments.
The diffuse source appears to have had an unusual origin and we discuss
possible mechanisms. We examine whether the source could be re-energized relic
radio plasma or a buoyant synchrotron bubble that is a relic of activity in NGC
5419. The more exciting prospect is that the source is relic plasma preserved
in the cluster gaseous environment following the chance injection of a radio
lobe into the ICM as a result of activity in a galaxy at the periphery of the
cluster.Comment: 26 pages, 8 figures, accepted for publication in the Astronomical
Journa
VLA Observations of the "Eye of the Tornado"- the High Velocity \HII Region G357.63-0.06
The unusual supernova remnant candidate G357.7-0.1 and the compact source
G357.63-0.06 have been observed with the Very Large Array at 1.4 and 8.3 GHz.
The H92 line (8.3 GHz) was detected from the compact source with a
surprising velocity of about -210 km/s indicating that this source is an \HII
region, is most likely located at the Galactic center, and is unrelated to the
SNR. The \HI absorption line (1.4 GHz) data toward these sources supports this
picture and suggests that G357.7-0.1 lies farther away than the Galactic
center.Comment: Latex, 14 pages including 4 figures. Accepted to A
The Sizes of 1720 MHz OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28
We have used the NRAO Very Long Baseline Array (VLBA) to image OH(1720 MHz)
masers in the supernova remnants W28 and W44 at a resolution of 40 mas. We also
used MERLIN to observe the same OH(1720 MHz) masers in W44 at a resolution of
290 x 165 mas. All the masers are resolved by these VLBA and MERLIN
observations. The measured sizes range from 50 to 180 mas and yield brightness
temperature estimates from 0.3--20 x 10**8 K. We investigate whether these
measured angular sizes are intrinsic and hence originate as a result of the
physical conditions in the supernova remnant shock, or whether they are scatter
broadened sizes produced by the turbulent ionized gas along the line of sight.
While the current data on the temporal and angular broadening of pulsars,
masers and extragalactic soures toward W44 and W28 can be understood in terms
of scattering, we cannot rule out that these large sizes are intrinsic. Recent
theoretical modeling by Lockett et al. suggests that the physical parameters in
the shocked region are indicative of densities and OH abundances which lead to
estimates of sizes as large as what we measure. If the sizes and structure are
intrinsic, then the OH(1720 MHz) masrs may be more like the OH(1612 MHz) masers
in circumstellar shells than OH masers associated with HII regions. At two
locations in W28 we observe the classical S-shapes in the Stokes V profiles
caused by Zeeman splitting and use it to infer magnetic fields of order 2
milliGauss.Comment: 24 pages, 6 figures, accepted by Ap
Truncated-Determinant Diagrammatic Monte Carlo for Fermions with Contact Interaction
For some models of interacting fermions the known solution to the notorious
sign-problem in Monte Carlo (MC) simulations is to work with macroscopic
fermionic determinants; the price, however, is a macroscopic scaling of the
numerical effort spent on elementary local updates. We find that the {\it
ratio} of two macroscopic determinants can be found with any desired accuracy
by considering truncated (local in space and time) matices. In this respect, MC
for interacting fermionic systems becomes similar to that for the
sign-problem-free bosonic systems with system-size independent update cost. We
demonstrate the utility of the truncated-determinant method by simulating the
attractive Hubbard model within the MC scheme based on partially summed Feynman
diagrams. We conjecture that similar approach may be useful in other
implementations of the sign-free determinant schemes.Comment: results of the actual Hubbard model simulations are adde
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